Begin directory contrib docs and split commands (#3650)

* Begin directory contrib docs and split commands

* Fix unused import warning

crates/nu-command/src/commands/strings/parse/command.rs

@@ -0,0 +1,212 @@
+use crate::prelude::*;
+use nu_engine::WholeStreamCommand;
+use nu_errors::ShellError;
+use nu_protocol::{Signature, SyntaxShape, TaggedDictBuilder, UntaggedValue, Value};
+use nu_source::Tagged;
+
+use regex::{self, Regex};
+
+pub struct Command;
+
+impl WholeStreamCommand for Command {
+    fn name(&self) -> &str {
+        "parse"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("parse")
+            .required(
+                "pattern",
+                SyntaxShape::String,
+                "the pattern to match. Eg) \"{foo}: {bar}\"",
+            )
+            .switch("regex", "use full regex syntax for patterns", Some('r'))
+    }
+
+    fn usage(&self) -> &str {
+        "Parse columns from string data using a simple pattern."
+    }
+
+    fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
+        operate(args)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        let mut row = IndexMap::new();
+        row.insert("foo".to_string(), Value::from("hi"));
+        row.insert("bar".to_string(), Value::from("there"));
+        vec![
+            Example {
+                description: "Parse a string into two named columns",
+                example: "echo \"hi there\" | parse \"{foo} {bar}\"",
+                result: Some(vec![UntaggedValue::row(row.clone()).into()]),
+            },
+            Example {
+                description: "Parse a string using regex pattern",
+                example: "echo \"hi there\" | parse -r \"(?P<foo>\\w+) (?P<bar>\\w+)\"",
+                result: Some(vec![UntaggedValue::row(row).into()]),
+            },
+        ]
+    }
+}
+
+pub fn operate(args: CommandArgs) -> Result<OutputStream, ShellError> {
+    let name_tag = args.call_info.name_tag.clone();
+
+    let pattern: Tagged<String> = args.req(0)?;
+    let regex: bool = args.has_flag("regex");
+
+    let item_to_parse = if regex {
+        pattern.item.clone()
+    } else {
+        build_regex(&pattern.item, pattern.tag.clone())?
+    };
+
+    let regex_pattern =
+        Regex::new(&item_to_parse).map_err(|e| parse_regex_error(e, pattern.span()))?;
+
+    let columns = column_names(&regex_pattern);
+    let mut parsed: VecDeque<Value> = VecDeque::new();
+
+    for v in args.input {
+        match v.as_string() {
+            Ok(s) => {
+                let results = regex_pattern.captures_iter(&s);
+
+                for c in results {
+                    let mut dict = TaggedDictBuilder::new(&v.tag);
+
+                    for (column_name, cap) in columns.iter().zip(c.iter().skip(1)) {
+                        let cap_string = cap.map(|v| v.as_str()).unwrap_or("").to_string();
+                        dict.insert_untagged(column_name, UntaggedValue::string(cap_string));
+                    }
+
+                    parsed.push_back(dict.into_value());
+                }
+            }
+            Err(_) => {
+                return Err(ShellError::labeled_error_with_secondary(
+                    "Expected string input",
+                    "expected string input",
+                    &name_tag,
+                    "value originated here",
+                    v.tag,
+                ))
+            }
+        }
+    }
+
+    Ok(parsed.into_iter().into_output_stream())
+}
+
+fn build_regex(input: &str, tag: Tag) -> Result<String, ShellError> {
+    let mut output = "(?s)\\A".to_string();
+
+    //let mut loop_input = input;
+    let mut loop_input = input.chars().peekable();
+    loop {
+        let mut before = String::new();
+        while let Some(c) = loop_input.next() {
+            if c == '{' {
+                // If '{{', still creating a plaintext parse command, but just for a single '{' char
+                if loop_input.peek() == Some(&'{') {
+                    let _ = loop_input.next();
+                } else {
+                    break;
+                }
+            }
+            before.push(c);
+        }
+
+        if !before.is_empty() {
+            output.push_str(&regex::escape(&before));
+        }
+
+        // Look for column as we're now at one
+        let mut column = String::new();
+        while let Some(c) = loop_input.next() {
+            if c == '}' {
+                break;
+            }
+            column.push(c);
+
+            if loop_input.peek().is_none() {
+                return Err(ShellError::labeled_error(
+                    "Found opening `{` without an associated closing `}`",
+                    "invalid parse pattern",
+                    tag,
+                ));
+            }
+        }
+
+        if !column.is_empty() {
+            output.push_str("(?P<");
+            output.push_str(&column);
+            output.push_str(">.*?)");
+        }
+
+        if before.is_empty() && column.is_empty() {
+            break;
+        }
+    }
+
+    output.push_str("\\z");
+    Ok(output)
+}
+
+fn column_names(regex: &Regex) -> Vec<String> {
+    regex
+        .capture_names()
+        .enumerate()
+        .skip(1)
+        .map(|(i, name)| {
+            name.map(String::from)
+                .unwrap_or_else(|| format!("Capture{}", i))
+        })
+        .collect()
+}
+
+fn parse_regex_error(e: regex::Error, base_span: Span) -> ShellError {
+    match e {
+        regex::Error::Syntax(msg) => {
+            let mut lines = msg.lines();
+
+            let main_msg = lines
+                .next()
+                .map(|l| l.replace(':', ""))
+                .expect("invalid regex pattern");
+
+            let span = lines.nth(1).map(|l| l.find('^')).flatten().map(|space| {
+                let start = base_span.start() + space - 3;
+                Span::for_char(start)
+            });
+
+            let msg = lines
+                .next()
+                .map(|l| l.split(':').nth(1))
+                .flatten()
+                .map(|s| s.trim().to_string());
+
+            match (msg, span) {
+                (Some(msg), Some(span)) => {
+                    ShellError::labeled_error_with_secondary(&msg, &msg, span, main_msg, span)
+                }
+                _ => ShellError::labeled_error("Invalid regex", "invalid regex", base_span),
+            }
+        }
+        _ => ShellError::labeled_error("Invalid regex", "invalid regex", base_span),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Command;
+    use super::ShellError;
+
+    #[test]
+    fn examples_work_as_expected() -> Result<(), ShellError> {
+        use crate::examples::test as test_examples;
+
+        test_examples(Command {})
+    }
+}

crates/nu-command/src/commands/strings/parse/mod.rs

@@ -0,0 +1,3 @@
+mod command;
+
+pub use command::Command as Parse;